1. Technical Field
The present disclosure relates to a gas generator that mixes and burns a fuel and an oxidizer.
2. Description of the Related Art
In a rocket engine, a fuel and an oxidizer are each pressurized by a turbopump, and are supplied to a main combustion chamber. At this time, a part of the fuel and the oxidizer is introduced into a gas generator and is burned, and the resulting combustion gas is supplied as a turbine driving fluid for each of the turbopumps for fuel and oxidizer.
The combustion gas supplied from the gas generator to the turbopumps is required to have low temperatures from the viewpoint of durability of turbines of the turbopumps. Therefore, in the gas generator, the temperature of the combustion gas is suppressed by burning the fuel and the oxidizer at a mixture ratio in which the fuel is excessive.
Here, the mixture ratio between a fuel and an oxidizer represents a value obtained by dividing the mass flow rate of the oxidizer by the mass flow rate of the fuel. In the case where the mixture ratio falls outside an appropriate range to be in a state of an excess fuel amount, the mixture ratio becomes a low mixture ratio (fuel rich), whereas, in the case where the mixture ratio falls outside an appropriate range to be in a state of an excess oxidizer amount, the mixture ratio becomes a super-high mixture ratio (oxidizer rich).
Note that a state of excess fuel is near a flammable limit and deteriorates ignitability or flame-stability. Accordingly, in order to avoid insufficient combustion-gas output due to non-ignition or anti-inflammation, the mixture ratio is reduced by diluting, with fuel, the combustion gas obtained by combustion of a fuel and an oxidizer at a mixture ratio in an appropriate range, and thus temperature of the combustion gas is reduced (cf. see NASA SP-8081 “LIQUID PROPELLANT GAS GENERATORS” pp. 8-12).
Furthermore, as the gas generator in which the combustion gas obtained through combustion of a fuel and an oxidizer at a mixture ratio falling in an appropriate range is diluted with fuel, there is proposed a gas generator in which a plurality of injection elements each having like-impingement fuel injection nozzles is arranged at a central portion and on an outer peripheral concentric circle of the combustor, and a plurality of injection elements each having like-impingement oxidizer injection nozzle is arranged on a concentric circle between the central portion and the outer peripheral concentric circle (cf. Patent Japanese Patent Laid-Open Publication No. 2012-189014).
In the proposition, there is formed a high-temperature combustion zone in which equal amounts of a fuel and an oxidizer are injected at the central portion of the combustor, and there is formed a low-temperature combustion zone in which a fuel and an oxidizer are injected in a state of being excess fuel at an outer peripheral portion of the combustor.